The present invention relates to an apparatus which is selectively operable for either producing asphalt suitable for highway construction, or for the decontamination of petroleum contaminated soils and the like.
The effective cleanup and disposal of soils which are contaminated with petroleum products and other contaminates have recently become major environmental concerns. As one specific example of the problem, a large number of underground fuel tanks have been found to be leaking and releasing a variety of contaminates into the surrounding soil, and as these tanks are being removed and repaired pursuant to environmental regulations, the volume of contaminated soil has been growing. Many communities no longer permit such soil to be placed in landfills, and thus a need exists for the decontamination of the soils.
One method of decontamination is to simply incinerate the soil, but such thermal treatment is not completely effective since it tends to produce large quantities of nitrogen oxides which are released into the atmosphere, and which are believed to contribute to so-called acid rain. Also, thermal treatment alone is not totally effective for soils contaminated with non-volatile heavy metals, and the incineration of soils containing volatile metals in high concentrations also presents a significant problem of emissions into the atmosphere.
U.S. Pat. No. 4,815,398 to Keating et al discloses an apparatus for detoxifying soil wherein the soil is initially heated to a relatively low temperature in a rotary dryer so as to volatilize the contaminants, and the volatilized contaminants are then fed to a high temperature rotary kiln which converts the volatile contaminants to non-toxic products which are then released to the atmosphere. This system is seen to be more effective in avoiding the release of contaminants to the atmosphere as compared to the prior incineration systems, but the apparatus is relatively costly, and it is not economically suitable to periodically process relatively small amounts of contaminated soil.
It is accordingly an object of the present invention to provide an apparatus for effectively and economically decontaminating petroleum contaminated soils and the like.